Celestial photography equipment in celestial photography

Celestial photography does not need an astronomical telescope, as simple as a camera on a tripod. As for cameras, astrophotography can range from 135 SLR to 6x9 large negative camera. But a camera suitable for shooting all kinds of celestial bodies and phenomena should have the following characteristics:

Multi-stage shutter and B (light bulb) shutter can change the lens for a long time, and the connected telescope is light in weight. Based on the above conditions, 135 SLR can be said to be the most suitable for all kinds of celestial photography. It is best to buy a cable release with a lock, which can reduce vibration interference and can also replace door B or door T for long-term exposure. Fixed photography can be said to be the simplest celestial photography method, which does not need a telescope, and basically only needs a camera and a tripod. Cable release is sometimes used. Most cameras can be used for fixed photography, and it is important that cameras can be exposed for a long time (1 sec or more). Among them, 135 single mirror with B shutter is the most suitable. If the shutter rope is matched (and it can be locked automatically when pressed), it can be exposed for several hours. Some SLR mirrors can be operated with B shutter without battery, such as the famous Nikon FM2. During several hours of exposure, cameras using electronic shutters will consume considerable power. If the power supply is exhausted, the shutter will close and the exposure will stop. As for the general digital camera, the slowest shutter is only a few seconds to a minute, and you can take some constellation photos. If you want to shoot the stars, SLR is more suitable.

Camera performance requirements are not high. No exposure meter, autofocus, automatic exposure and automatic exposure are needed. Of course, you still need these functions when shooting a solar eclipse. But when shooting constellations, star trails, meteor showers and other objects, these functions are useless.

Almost all SLR mirrors can switch lenses according to the shooting purpose. As long as the aperture of the lens is not too small. The smaller the focal length of the lens, the wider the field of view, and the larger the range of the sky that can be photographed. Some people suggest that novices use standard lenses because they are generally cheaper and the quality is generally good. The optical quality of fixed-focus lens is generally better than that of zoom lens.

When shooting, first fix the camera on the tripod, and ensure that the focus is at infinity when focusing (the lens is marked with the word ∞). It should be noted that the infinity mark of some autofocus lenses does not match the real infinity position. Set the shutter to B, and press the shutter to expose the sky area to be photographed.

Fixed photography has many subjects to shoot. Constellations, star trails, eclipses, meteors and even auroras can all be photographed in a fixed way.

It takes only 5 to 30 seconds to take pictures of bright planets and constellations with fixed photography. Please open the lens aperture to the maximum (or reduce it by one level) when shooting, and the lens can range from fisheye to standard lens. If the environment permits, try to shoot at ISO 800, 1600 or even 3200. Users of digital cameras can take a photo before shooting, and then shoot with different exposure combinations. Because the starry sky has been turning from east to west, it is necessary to limit the exposure time in order to keep the stars dotted. Please see here for the exposure time limit. Magnification photography, like direct focus photography, belongs to tracking photography, but the exposure time is relatively short. However, magnification photography is greatly influenced by external factors, and it is the most difficult photography method to produce good works in all astrophotography.

Magnifying photographic equipment

The equipment for magnifying photography has great repeatability with the equipment for directly focusing photography. However, the enlarged photography does not need a guide star, which can save the cost of guide star, and in addition, you can buy an adapter for enlarged photography.

Camera part: digital SLR camera, cable release.

Telescope part: any kind of telescope (large aperture and long focal length is preferred), high-precision equatorial telescope.

Other related accessories: magnifying camera tube, magnifying projection eyepiece, recording equipment.

Of course, the bigger the telescope, the better. This is the truth, the longer the focal length, the better. This is because the longer the focal length, the easier it is to improve the magnification. In addition, magnifying photography needs to use eyepieces to magnify the images of celestial bodies, and the eyepieces used in magnifying photography are different from ordinary visual eyepieces. The quality of eyepiece used for magnifying projection will be better, but the price of eyepiece is higher.

1. Enlarge the subject.

Magnification photography mainly photographs parts of the surface of the planet, the sun and the moon, such as sunspots or a crater on the moon. This is because the apparent diameter of the planet is very small. If you only use the focal length of the telescope to shoot, the planet in the photo will be too small to see the surface of the planet. Therefore, you must enlarge the image of the planet with an eyepiece to see the appearance or changes of the planet surface. However, some people have magnified and photographed planetary nebulae with low-power eyepieces, mainly because the focal length of the telescope is not enough and the photographed nebulae are too small. This kind of shooting is quite difficult, and it is difficult to shoot well without considerable experience.

The way to enlarge photos.

The preparatory action of magnifying photography is the same as that of direct focus photography. First, set up the instrument (without star guiding equipment), do a good job of balance, aim at the positive axis, then find the target, and then press the shutter after completing framing and photometry. The only difference from direct focus photography is the way the camera is installed. The camera is not directly equipped with a telescope. There must be a connecting pipe between the telescope and the camera, which can connect the two and can be equipped with an eyepiece. The author calls this thing a magnifying photographic connecting tube. After the telescope, connect the magnifying camera first, then the camera. Put a low-power eyepiece in the lens barrel to find the celestial body to be photographed, then change it into a high-power eyepiece, focus on the camera and press the shutter. Simple, right?

3. The problem of magnifying photography.

If only it were that simple. On earth, we need air to survive, but it is this kind of atmosphere that seriously interferes with astronomical observation and photography. We know two things first: first, air disturbance will make the stars shake, which will make the picture unclear. Second, the short focal length field of vision is wide, and the long focal length field of vision is narrow. The reason why the eyepiece is used for magnifying photography is because the focal length of the telescope is not long enough, and the magnifying function of the eyepiece must be used, which is equivalent to the extension of the focal length. With the increase of focal length, the viewing range is very small, so as long as there is a little air disturbance, it will be obvious in the telescope. Therefore, in order to make a good enlarged photographic work, besides strength, we have to know the face of God.

The second problem of magnifying photography is the tracking accuracy of equatorial telescope. As mentioned above, the planet is too small, so we should enlarge it with an eyepiece (that is, extend the focal length). When our magnification is particularly large, the extended focal length is about tens of thousands of millimeters. If the polar axis of the equatorial telescope is incorrect or the tracking accuracy of the equatorial telescope is not enough, it goes without saying that exposure is only a few seconds, even if it is as short as one second, it will affect the clarity (that is, resolution) of shooting celestial bodies. In addition, the aperture of telescopes suitable for magnifying photography is not small, so an adequate equatorial telescope is extremely necessary.

The third problem is very strange, it is vibration-not the vibration of the ground or telescope, but the vibration of the camera mirror. There is a mirror in the SLR camera, and the mirror will bounce up when the shutter is pressed, causing the camera to vibrate (or the telescope to vibrate). The darker the celestial body, the less sensitive it is to this action, but it will have a great impact on the planet or the moon. Therefore, if the mirror of the camera can bounce up and lock before exposure, this camera is more suitable for magnifying photography.

The fourth problem is focusing. When we zoom in on the planet with a high-powered eyepiece, the planet becomes very dark and it is difficult to focus. In addition to using a brighter focus screen, you can only take more shots to accumulate experience.

Now there is a way to solve the above problems, which is to use high sensitivity. We can shoot the planet or the moon with 400-degree or even 800-degree film, and still get good results. You can also use high sensitivity to shorten the exposure time and overcome the problems of atmospheric disturbance and tracking error, which can kill two birds with one stone.

Astrophotography generally refers to optical astrophotography, which can be divided into three aspects from the shooting of celestial bodies: detailed photography of stars in the solar system, photography of constellations and meteor showers, and photography of deep space nebulae.